The objective of the proposed study is to understand in chemical terms the biologial activities of a number of erythrocyte redox proteins - cytochrome b5, S-protein, a cyanide-binding protein, hemeprotein 565, and a pink copper protein. To achieve this objective it will be necessary to purify each protein to homogeneity, observe its physical properties, establish its composition and the nature of its active site, assign the biological activity, and finally elucidate its mechanism of action. The search for the origin, the enzymatic activity, and the biological significance of each of these proteins will include assaying the proteins for a number of redox activities which are expected to be present in the erythrocyte. The search will also involve the immunological, spectral, and chemical comparison of the erythrocyte proteins with proteins from liver cells. Particular emphasis will be placed on studying: the role of cytochrome b5 in methemoglobin reduction; the relationship of S-protein to cytochrome P-450; the relationship of the cyanide-binding protein to fatty acyl CoA desaturase; and the possibility that the pink copper protein is related to an amine oxidase.